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strrand.go
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strrand.go
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package strrand
import (
"fmt"
"math/rand"
"regexp"
"strconv"
"strings"
"time"
)
// RandomString returns random string from pattern
func RandomString(pattern string) (string, error) {
return New().Generate(pattern)
}
type picker interface {
pick() string
}
func makeRange(from rune, to rune) (r []string) {
for i := from; i <= to; i++ {
r = append(r, string(i))
}
return r
}
func concat(ss ...[]string) (r []string) {
for _, s := range ss {
r = append(r, s...)
}
return r
}
type chrPicker []string
func (p chrPicker) pick() string {
if len(p) < 1 {
return ""
}
idx := rand.Intn(len(p))
return p[idx]
}
type variantPicker struct {
min uint64
max uint64
picker picker
}
func (vp variantPicker) pick() (str string) {
num := vp.decidePickNum()
for i := 0; i < num; i++ {
str += vp.picker.pick()
}
return str
}
func (vp variantPicker) decidePickNum() int {
if vp.max < vp.min {
return 0
}
return int(vp.min) + rand.Intn(int(vp.max-vp.min)+1)
}
func init() {
rand.Seed(time.Now().UnixNano())
}
var upper chrPicker = makeRange('A', 'Z')
var lower chrPicker = makeRange('a', 'z')
var digit chrPicker = makeRange('0', '9')
var punct chrPicker = concat(makeRange(33, 47), makeRange(58, 64), makeRange(91, 96), makeRange(123, 126))
var any chrPicker = concat(upper, lower, digit, punct)
var patterns = map[string]chrPicker{
"d": chrPicker(digit),
"D": chrPicker(concat(upper, lower, punct)),
"w": chrPicker(concat(upper, lower, digit, []string{"_"})),
// W: punct without '_'
"W": chrPicker(concat(makeRange(33, 47), makeRange(58, 64), makeRange(91, 94), makeRange(96, 96), makeRange(123, 126))),
"s": chrPicker([]string{" ", "\t"}),
"S": chrPicker(concat(upper, lower, digit, punct)),
// these are translated to their double quoted equivalents.
"t": chrPicker([]string{"\t"}),
"n": chrPicker([]string{"\n"}),
"r": chrPicker([]string{"\r"}),
"f": chrPicker([]string{"\f"}),
"a": chrPicker([]string{"\a"}),
"e": chrPicker([]string{string(27)}), // escape character
}
// Strrand factory object of random string generator
type Strrand struct {
Max uint
}
// Generator generating random strings
type Generator interface {
Generate() string
}
type pickers []picker
func (pis pickers) Generate() string {
result := ""
for _, p := range pis {
result += p.pick()
}
return result
}
// New returns Strrand struct
func New() *Strrand {
return &Strrand{}
}
var defaultMax uint = 10
func (sr *Strrand) max() uint {
if sr.Max < 1 {
return defaultMax
}
return sr.Max
}
// Generate generates random string
func (sr *Strrand) Generate(pattern string) (string, error) {
result := ""
g, err := sr.CreateGenerator(pattern)
if err != nil {
return result, err
}
return g.Generate(), nil
}
// CreateGenerator returns random string generator
func (sr *Strrand) CreateGenerator(pattern string) (Generator, error) {
pis := pickers([]picker{})
chars := func() *[]string {
c := strings.Split(pattern, "")
return &c
}()
for len(*chars) > 0 {
chr := (*chars)[0]
*chars = (*chars)[1:]
switch chr {
case "\\":
p, err := sr.handleEscape(chars)
if err != nil {
return nil, err
}
pis = append(pis, p)
case ".":
pis = append(pis, any)
case "[":
p, err := sr.handleBracket(chars)
if err != nil {
return nil, err
}
pis = append(pis, p)
case "*":
*chars = append(strings.Split("{0,}", ""), (*chars)...)
case "+":
*chars = append(strings.Split("{1,}", ""), (*chars)...)
case "?":
*chars = append(strings.Split("{0,1}", ""), (*chars)...)
case "{":
if len(pis) < 1 {
return pis, fmt.Errorf("invalid bracket")
}
pop := pis[len(pis)-1]
pis = pis[:len(pis)-1]
p, err := sr.handleBrace(chars, pop)
if err != nil {
return pis, err
}
pis = append(pis, p)
default:
pis = append(pis, chrPicker([]string{chr}))
}
}
return pis, nil
}
func (sr *Strrand) handleEscape(chars *[]string) (picker, error) {
if len(*chars) < 1 {
return chrPicker([]string{}), fmt.Errorf("regex not terminated")
}
chr := (*chars)[0]
*chars = (*chars)[1:]
if val, ok := patterns[chr]; ok {
return val, nil
}
switch chr {
case "x":
if len(*chars) < 2 {
return nil, fmt.Errorf("invalid hex format")
}
hex := (*chars)[0] + (*chars)[1]
*chars = (*chars)[2:]
c, err := strconv.ParseInt(hex, 16, 32)
if err != nil {
return nil, err
}
return chrPicker([]string{string(c)}), nil
default:
return chrPicker([]string{chr}), nil
}
}
func (sr *Strrand) handleBracket(chars *[]string) (picker, error) {
p := chrPicker([]string{})
escaped := false
rangeJustFinished := false
startChr := ""
for {
if len(*chars) < 1 {
return nil, fmt.Errorf("unmatched []")
}
chr := (*chars)[0]
*chars = (*chars)[1:]
if !escaped {
if chr == "]" {
break
}
if chr == `\` {
escaped = true
continue
}
if chr == "-" && len(p) > 0 {
if rangeJustFinished {
return nil, fmt.Errorf("invalid range")
}
startChr = p[len(p)-1]
p = p[:len(p)-1]
continue
}
}
escaped = false
if startChr != "" {
r := makeRange(([]rune(startChr))[0], ([]rune(chr))[0])
p = append(p, r...)
rangeJustFinished = true
startChr = ""
continue
}
rangeJustFinished = false
p = append(p, chr)
}
return p, nil
}
var rangeChrRe = regexp.MustCompile(`[0-9,]`)
var rangeRe = regexp.MustCompile(`^([0-9]+),([0-9]+)?$`)
func (sr *Strrand) handleBrace(chars *[]string, p picker) (picker, error) {
hasComma := false
buf := ""
for {
if len(*chars) < 1 {
return nil, fmt.Errorf("bad range %s", buf)
}
chr := (*chars)[0]
*chars = (*chars)[1:]
if chr == "}" {
break
}
if !rangeChrRe.MatchString(chr) {
return nil, fmt.Errorf("'%s' inside {} not supported", chr)
}
if chr == "," {
hasComma = true
}
buf += chr
}
var min, max uint64
if hasComma {
matches := rangeRe.FindStringSubmatch(buf)
if len(matches) == 0 {
return nil, fmt.Errorf("malformed range: {%s}", buf)
}
min, _ = strconv.ParseUint(matches[1], 10, 64)
if matches[2] == "" {
max = uint64(sr.max())
} else {
max, _ = strconv.ParseUint(matches[2], 10, 64)
}
if max < min {
return nil, fmt.Errorf("bad range {%s}", buf)
}
} else {
min, _ = strconv.ParseUint(buf, 10, 64)
max = min
}
return variantPicker{
max: max,
min: min,
picker: p,
}, nil
}